Stoke boss Mark Hughes has confirmed striker Saido Berahino served a suspension before he joined the club.
The Daily Mail has reported Berahino tested positive for a recreational drug during his time at West Brom.
Berahino signed for Stoke last month after completing the ban.
Hughes, speaking at a press conference covered by the club's website, www.stokecityfc.com, said: "We are aware of it clearly - there was an FA disciplinary matter and Saido had an eight-week suspension, I believe. We were aware of that before we signed him.
In terms of more detail you would probably need to refer back to his former club. We aren't in a position to give any more details as we don't have them.
"He had issues at his previous club for 18 months, which this is obviously a part of.
"As with all players we did our research on him before we signed him, but that didn't change our thinking at all.
"We are pleased with what he is producing and he is looking forward to the game tomorrow."
Striker Berahino, 23, was involved in a long contract dispute with West Brom before the club sanctioned his £12million sale.
It is reported the former England Under-21 international tested positive for a banned substance during an out-of-competition test in September.
Berahino did not play any competitive football between West Brom's Premier League game at Bournemouth on September 10 and making his Stoke debut in Wednesday's clash with Everton.
He could now make his second appearance for the Potters against his old club as Stoke travel to West Brom on Saturday.
Hughes said: "Why wouldn't I play him? He is in line to be involved. He came on to good effect on Wednesday and there is no reason why he shouldn't be involved tomorrow.
"He is itching to play a part, although the way the game is going will determine whether he comes on. Most opposition players get some stick, and he will get some I am sure, but he is of the view that he is probably used to having some stick from West Brom supporters."
The Football Association has declined to comment on the matter.
Berahino's career stalled at West Brom after a potential move to Tottenham collapsed in 2015 but Hughes is confident he can get back on track at the bet365 Stadium.
He said: "We have brought in a player with great ability, of a good age who hasn't reached his peak yet. He still has a lot of development to come, and we feel that what we can offer him here, it will benefit him.
"He will prosper here, I am sure of that and that is why we chased him for so long. The next three or four years are going to be really important for him, and for us. He wants to improve."